U.S. patent application number 16/061644 was filed with the patent office on 2019-09-05 for method and wireless device for transmitting random-access preamble by means of single-tone method.
This patent application is currently assigned to LG ELECTRONICS INC.. The applicant listed for this patent is LG ELECTRONICS INC.. Invention is credited to Daesung HWANG, Seunggye HWANG, Bonghoe KIM, Yunjung YI.
Application Number | 20190274168 16/061644 |
Document ID | / |
Family ID | 59056962 |
Filed Date | 2019-09-05 |
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United States Patent
Application |
20190274168 |
Kind Code |
A1 |
HWANG; Daesung ; et
al. |
September 5, 2019 |
METHOD AND WIRELESS DEVICE FOR TRANSMITTING RANDOM-ACCESS PREAMBLE
BY MEANS OF SINGLE-TONE METHOD
Abstract
Disclosed is a method for a wireless device for transmitting a
random-access preamble. The method may comprise the steps of:
generating a sequence of a random-access preamble; and mapping the
sequence of a random-access preamble to one sub-carrier wave from
among 12 sub-carrier waves of a frequency domain. The mapping step
may comprise the step for carrying out a first hop between a
plurality of sub-regions. Each sub-region may comprise a previously
set number of sub-carrier waves. The mapping step may additionally
comprise the step for carrying out a second hop from among the
sub-carrier waves within any one sub-region.
Inventors: |
HWANG; Daesung; (Seoul,
KR) ; YI; Yunjung; (Seoul, KR) ; KIM;
Bonghoe; (Seoul, KR) ; HWANG; Seunggye;
(Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
|
KR |
|
|
Assignee: |
LG ELECTRONICS INC.
Seoul
KR
|
Family ID: |
59056962 |
Appl. No.: |
16/061644 |
Filed: |
November 29, 2016 |
PCT Filed: |
November 29, 2016 |
PCT NO: |
PCT/KR2016/013838 |
371 Date: |
June 12, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62269102 |
Dec 18, 2015 |
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62277006 |
Jan 11, 2016 |
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62288400 |
Jan 28, 2016 |
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62306600 |
Mar 10, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 27/2602 20130101;
H04L 5/0053 20130101; H04L 5/0012 20130101; H04W 74/0833 20130101;
H04W 74/004 20130101; H04W 74/006 20130101 |
International
Class: |
H04W 74/08 20060101
H04W074/08; H04L 5/00 20060101 H04L005/00; H04W 74/00 20060101
H04W074/00 |
Claims
1. A method for transmitting a random access preamble, the method
performed by a wireless device and comprising: generating a
sequence of a random access preamble; and mapping the sequence of
the random access preamble onto one subcarrier among 12 subcarriers
in a frequency domain, transmitting the sequence of the random
access preamble which is mapped onto the one subcarrier; wherein
the mapping includes: performing a first hopping among plural
groups, each of which includes a pre-configured number of
subcarriers, and performing a second hopping among the
pre-configured number of subcarriers in one group of the plural
groups.
2. The method of claim 1, wherein the performing of the first
hopping comprises: selecting one group among the plural groups; and
performing a hopping into the selected group.
3. The method of claim 2, wherein the performing of the second
hopping comprises: selecting one subcarrier among plural
subcarriers included in the selected group; performing a hopping
into the selected subcarrier; and mapping the sequence of the
random access preamble onto the selected subcarrier.
4. The method of claim 1, further comprising: receiving information
on one or more of the plural groups via a higher layer signal.
5. The method of claim 4, wherein the information on one or more of
the plural groups received via the higher layer signal includes
information on the pre-configured number of the subcarriers
included in each group.
6. The method of claim 5, wherein the information on one or more of
the plural groups received via the higher layer signal includes
information on a frequency offset.
7. The method of claim 1, wherein the sequence of the random access
preamble is generated based on an identifier of a narrowband
internet of things (NB-IoT).
8. The method of claim 1, further comprising: receiving a physical
downlink control channel (PDCCH) order for triggering a
transmission of the random access preamble.
9. The method of claim 8, wherein the PDCCH order includes downlink
control information (DCI) including information on a subcarrier on
which the random access preamble is transmitted.
10. A wireless device for transmitting a random access preamble,
the wireless device comprising: a transceiver; and a processor
configured to control the transceiver and configured to: generate a
sequence of a random access preamble; map the sequence of the
random access preamble onto one subcarrier among 12 subcarriers in
a frequency domain, control the transceiver to transmit the
sequence of the random access preamble which is mapped onto the one
subcarrier; wherein the mapping of the processor includes:
performing a first hopping among plural groups, each of which
includes a pre-configured number of subcarriers, and performing a
second hopping among the pre-configured number of subcarriers in
one group of the plural groups.
11. The wireless device of claim 10, wherein for performing the
first hopping, the processor is further configured to: select one
group among the plural groups; and perform a hopping into the
selected group.
12. The wireless device of claim 11, wherein for performing the
second hopping, the processor is further configured to: select one
subcarrier among plural subcarriers included in the selected group;
perform a hopping into the selected subcarrier; and map the
sequence of the random access preamble onto the selected
subcarrier.
13. The wireless device of claim 10, wherein the transceiver is
configured to: receive information on one or more of the plural
groups via a higher layer signal.
14. The wireless device of claim 10, wherein the transceiver is
configured to: receive a physical downlink control channel (PDCCH)
order for triggering a transmission of the random access
preamble.
15. The wireless device of claim 14, wherein the PDCCH order
includes downlink control information (DCI) including information
on a subcarrier on which the random access preamble is transmitted.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to mobile communication.
Related Art
[0002] 3rd generation partnership project (3GPP) long term
evolution (LTE) evolved from a universal mobile telecommunications
system (UMTS) is introduced as the 3GPP release 8. The 3GPP LTE
uses orthogonal frequency division multiple access (OFDMA) in a
downlink, and uses single carrier-frequency division multiple
access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input
multiple output (MIMO) having up to four antennas. In recent years,
there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) evolved
from the 3GPP LTE.
[0003] As disclosed in 3GPP TS 36.211 V10.4.0 (2011-12) "Evolved
Universal Terrestrial Radio Access (E-UTRA); Physical Channels and
Modulation (Release 10)", a physical channel of LTE may be
classified into a downlink channel, i.e., a PDSCH (Physical
Downlink Shared Channel) and a PDCCH (Physical Downlink Control
Channel), and an uplink channel, i.e., a PUSCH (Physical Uplink
Shared Channel) and a PUCCH (Physical Uplink Control Channel).
[0004] Recently, IoT (Internet of Things) communication has
attracted attention. The IoT refers to communications that do not
involve human interaction. There is a dissection about trying to
accommodate such IoT communications in a cellular-based LTE
system.
[0005] However, since the legacy LTE system has been designed for
the purpose of supporting high-speed data communication, such an
LTE system has been regarded as an expensive communication
system.
[0006] However, the IoT communication is required to be implemented
at a low price because of its characteristics, so that it may be
widely used.
[0007] Thus, discussions about reducing bandwidth have been for
cost reduction. However, an IoT device operating in a reduced band
may perform communication in an area with a poor channel
environment (e.g., under a bridge, under the sea, or on the sea)
and thus can use repeated transmission or power boosting
techniques. Power boosting may be a method in which a frequency
domain is reduced and power is concentrated on a particular
frequency resource. For example, when one RB includes 12 REs,
transmission may be performed by concentrating power on a
particular RE in a particular RB, instead of through a plurality of
RBs.
[0008] A method of performing communication by concentrating power
on one RE in a RB may be collectively referred to as a single-tone
transmission method.
[0009] However, the single-tone transmission method is not
currently supported by the 3GPP standard. In particular, according
to the current 3GPP standard, a random access preamble for initial
access is designed to be transmitted through one RB, that is, 12
subcarriers.
SUMMARY OF THE INVENTION
[0010] Accordingly, a disclosure of the present specification has
been made in an effort to solve the aforementioned problem.
[0011] To achieve the foregoing purposes, the disclosure of the
present invention proposes a method for transmitting a random
access preamble. The method may be performed by a wireless device
and comprise: generating a sequence of a random access preamble;
mapping the sequence of the random access preamble onto one
subcarrier among 12 subcarriers in a frequency domain. The mapping
may include: performing a first hopping among plural sub-regions,
each of which includes a pre-configured number of subcarriers, and
performing a second hopping among the pre-configured number
subcarriers in one sub-region.
[0012] The performing of the first hopping may comprise: selecting
one sub-region among the plural sub-regions; and performing a
hopping into the selected sub-region.
[0013] The performing of the second hopping may comprise: selecting
one subcarrier among plural subcarriers included in the selected
sub-region; performing a hopping into the selected subcarrier; and
mapping the sequence of the random access preamble onto the
selected subcarrier.
[0014] The method may further comprise: receiving information on
the sub-regions via a higher layer signal.
[0015] The information on the sub-regions received via the higher
layer signal may include: information on the pre-configured number
of the subcarriers included in each sub-region.
[0016] The information on the sub-regions received via the higher
layer signal may include: information on a frequency offset.
[0017] The sequence of the random access preamble may be generated
based on an identifier of a narrowband internet of things
(NB-IoT).
[0018] The method may further comprise: receiving a physical
downlink control channel (PDCCH) order for triggering a
transmission of the random access preamble.
[0019] The PDCCH order may include: downlink control information
(DCI) including information on a subcarrier on which the random
access preamble is transmitted.
[0020] To achieve the foregoing purposes, the disclosure of the
present invention also proposes a wireless device for transmitting
a random access preamble. The wireless device may comprise: a
transceiver; and a processor configured to control the transceiver
and configured to: generate a sequence of a random access preamble;
map the sequence of the random access preamble onto one subcarrier
among 12 subcarriers in a frequency domain. The mapping of the
processor may include: performing a first hopping among plural
sub-regions, each of which includes a pre-configured number of
subcarriers, and performing a second hopping among the
pre-configured number subcarriers in one sub-region.
[0021] According to the disclosure of the present specification,
the problems of the above-described prior art are solved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a wireless communication system.
[0023] FIG. 2 illustrates a structure of a radio frame according to
FDD in 3GPP LTE.
[0024] FIG. 3 illustrates a structure of a downlink radio frame
according to TDD in the 3GPP LTE.
[0025] FIG. 4 is an exemplary diagram illustrating a resource grid
for one uplink or downlink slot in the 3GPP LTE.
[0026] FIG. 5 is a flowchart illustrating a random access procedure
in 3GPP LTE.
[0027] FIG. 6A shows an example of IoT (Internet of Things)
communication.
[0028] FIG. 6B is an example of a cell coverage extension or
enhancement for an IoT device.
[0029] FIGS. 7A and 7B are views illustrating examples of a
sub-band in which an IoT device operates.
[0030] FIG. 8 shows an example of a time resource used for NB-IoT
on M-frames basis.
[0031] FIG. 9 shows another example of a time resource and a
frequency resource that may be used for an NB IoT device.
[0032] FIGS. 10A and 10B illustrate a first example of a first
embodiment of the present specification. FIG. 10C illustrates a
second example, and FIG. 10D illustrates a third example.
[0033] FIG. 11 illustrates an example of transmission of a symbol
which is a frequency resource unit for transmission of a PRACH
signal (e.g., a random access preamble).
[0034] FIGS. 12A to 12C illustrate examples in which a time
resource unit for a PRACH signal (e.g., a random access preamble)
is 1.3 ms when a subframe has a length of 1 ms and when a subframe
has a length of 4 ms.
[0035] FIG. 13A illustrates a first example of a second embodiment
of the present specification. FIG. 13B illustrates a third
example.
[0036] FIG. 14 illustrates a fourth example among a plurality of
examples of a third embodiment of the present specification.
[0037] FIG. 15 is a flowchart illustrating the operation of a
wireless device according to the fourth example of the third
embodiment of the present specification.
[0038] FIG. 16 is a block diagram illustrating a wireless
communication system to implement embodiments of the present
specification.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0039] Hereinafter, based on 3rd Generation Partnership Project
(3GPP) long term evolution (LTE) or 3GPP LTE-advanced (LTE-A), the
present invention will be applied. This is just an example, and the
present invention may be applied to various wireless communication
systems. Hereinafter, LTE includes LTE and/or LTE-A.
[0040] The technical terms used herein are used to merely describe
specific embodiments and should not be construed as limiting the
present invention. Further, the technical terms used herein should
be, unless defined otherwise, interpreted as having meanings
generally understood by those skilled in the art but not too
broadly or too narrowly. Further, the technical terms used herein,
which are determined not to exactly represent the spirit of the
invention, should be replaced by or understood by such technical
terms as being able to be exactly understood by those skilled in
the art. Further, the general terms used herein should be
interpreted in the context as defined in the dictionary, but not in
an excessively narrowed manner.
[0041] The expression of the singular number in the present
invention includes the meaning of the plural number unless the
meaning of the singular number is definitely different from that of
the plural number in the context. In the following description, the
term `include` or `have` may represent the existence of a feature,
a number, a step, an operation, a component, a part or the
combination thereof described in the present invention, and may not
exclude the existence or addition of another feature, another
number, another step, another operation, another component, another
part or the combination thereof.
[0042] The terms `first` and `second` are used for the purpose of
explanation about various components, and the components are not
limited to the terms `first` and `second`. The terms `first` and
`second` are only used to distinguish one component from another
component. For example, a first component may be named as a second
component without deviating from the scope of the present
invention.
[0043] It will be understood that when an element or layer is
referred to as being "connected to" or "coupled to" another element
or layer, it can be directly connected or coupled to the other
element or layer or intervening elements or layers may be present.
In contrast, when an element is referred to as being "directly
connected to" or "directly coupled to" another element or layer,
there are no intervening elements or layers present.
[0044] Hereinafter, exemplary embodiments of the present invention
will be described in greater detail with reference to the
accompanying drawings. In describing the present invention, for
ease of understanding, the same reference numerals are used to
denote the same components throughout the drawings, and repetitive
description on the same components will be omitted. Detailed
description on well-known arts which are determined to make the
gist of the invention unclear will be omitted. The accompanying
drawings are provided to merely make the spirit of the invention
readily understood, but not should be intended to be limiting of
the invention. It should be understood that the spirit of the
invention may be expanded to its modifications, replacements or
equivalents in addition to what is shown in the drawings.
[0045] As used herein, `base station` generally refers to a fixed
station that communicates with a wireless device and may be denoted
by other terms such as eNB (evolved-NodeB), BTS (base transceiver
system), or access point.
[0046] As used herein, `user equipment (UE)` may be stationary or
mobile, and may be denoted by other terms such as device, wireless
device, terminal, MS (mobile station), UT (user terminal), SS
(subscriber station), MT (mobile terminal) and etc.
[0047] FIG. 1 illustrates a wireless communication system.
[0048] As seen with reference to FIG. 1, the wireless communication
system includes at least one base station (BS) 20. Each base
station 20 provides a communication service to specific
geographical areas (generally, referred to as cells) 20a, 20b, and
20c. The cell can be further divided into a plurality of areas
(sectors).
[0049] The UE generally belongs to one cell and the cell to which
the UE belong is referred to as a serving cell. A base station that
provides the communication service to the serving cell is referred
to as a serving BS. Since the wireless communication system is a
cellular system, another cell that neighbors to the serving cell is
present. Another cell which neighbors to the serving cell is
referred to a neighbor cell. A base station that provides the
communication service to the neighbor cell is referred to as a
neighbor BS. The serving cell and the neighbor cell are relatively
decided based on the UE.
[0050] Hereinafter, a downlink means communication from the base
station 20 to the UE1 10 and an uplink means communication from the
UE 10 to the base station 20. In the downlink, a transmitter may be
a part of the base station 20 and a receiver may be a part of the
UE 10. In the uplink, the transmitter may be a part of the UE 10
and the receiver may be a part of the base station 20.
[0051] Meanwhile, the wireless communication system may be
generally divided into a frequency division duplex (FDD) type and a
time division duplex (TDD) type. According to the FDD type, uplink
transmission and downlink transmission are achieved while occupying
different frequency bands. According to the TDD type, the uplink
transmission and the downlink transmission are achieved at
different time while occupying the same frequency band. A channel
response of the TDD type is substantially reciprocal. This means
that a downlink channel response and an uplink channel response are
approximately the same as each other in a given frequency area.
Accordingly, in the TDD based wireless communication system, the
downlink channel response may be acquired from the uplink channel
response. In the TDD type, since an entire frequency band is
time-divided in the uplink transmission and the downlink
transmission, the downlink transmission by the base station and the
uplink transmission by the terminal may not be performed
simultaneously. In the TDD system in which the uplink transmission
and the downlink transmission are divided by the unit of a
subframe, the uplink transmission and the downlink transmission are
performed in different subframes.
[0052] Hereinafter, the LTE system will be described in detail.
[0053] FIG. 2 shows a downlink radio frame structure according to
FDD of 3rd generation partnership project (3GPP) long term
evolution (LTE).
[0054] The radio frame of FIG. 2 may be found in the section 5 of
3GPP TS 36.211 V10.4.0 (2011-12) "Evolved Universal Terrestrial
Radio Access (E-UTRA); Physical Channels and Modulation (Release
10)".
[0055] The radio frame includes 10 subframes indexed 0 to 9. One
subframe includes two consecutive slots. Accordingly, the radio
frame includes 20 slots. The time taken for one subframe to be
transmitted is denoted TTI (transmission time interval). For
example, the length of one subframe may be 1 ms, and the length of
one slot may be 0.5 ms.
[0056] The structure of the radio frame is for exemplary purposes
only, and thus the number of subframes included in the radio frame
or the number of slots included in the subframe may change
variously.
[0057] Meanwhile, one slot may include a plurality of OFDM symbols.
The number of OFDM symbols included in one slot may vary depending
on a cyclic prefix (CP).
[0058] FIG. 3 illustrates the architecture of a downlink radio
frame according to TDD in 3GPP LTE.
[0059] For this, 3GPP TS 36.211 V10.4.0 (2011-23) "Evolved
Universal Terrestrial Radio Access (E-UTRA); Physical Channels and
Modulation (Release 8)", Ch. 4 may be referenced, and this is for
TDD (time division duplex).
[0060] Subframes having index #1 and index #6 are denoted special
subframes, and include a DwPTS (Downlink Pilot Time Slot: DwPTS), a
GP (Guard Period) and an UpPTS (Uplink Pilot Time Slot). The DwPTS
is used for initial cell search, synchronization, or channel
estimation in a terminal. The UpPTS is used for channel estimation
in the base station and for establishing uplink transmission sync
of the terminal. The GP is a period for removing interference that
arises on uplink due to a multi-path delay of a downlink signal
between uplink and downlink.
[0061] In TDD, a DL (downlink) subframe and a UL (Uplink) co-exist
in one radio frame. Table 1 shows an example of configuration of a
radio frame.
TABLE-US-00001 TABLE 1 Switch- UL-DL point Subframe index
configuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S
U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms
D S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D
D D D D 6 5 ms D S U U U D S U U D
[0062] `D` denotes a DL subframe, `U` a UL subframe, and `S` a
special subframe. When receiving a UL-DL configuration from the
base station, the terminal may be aware of whether a subframe is a
DL subframe or a UL subframe according to the configuration of the
radio frame.
TABLE-US-00002 TABLE 2 Normal CP in downlink Extended CP in
downlink UpPTS UpPTS Special Normal Extended subframe CP in
Extended Normal CP CP in configuration DwPTS uplink CP in uplink
DwPTS in uplink uplink 0 6592 * Ts 2192 * Ts 2560 * Ts 7680 * Ts
2192 * Ts 2560 * Ts 1 19760 * Ts 20480 * Ts 2 21952 * Ts 23040 * Ts
3 24144 * Ts 25600 * Ts 4 26336 * Ts 7680 * Ts 4384 * Ts 5120 * ts
5 6592 * Ts 4384 * Ts 5120 * ts 20480 * Ts 6 19760 * Ts 23040 * Ts
7 21952 * Ts -- 8 24144 * Ts --
[0063] FIG. 4 illustrates an example resource grid for one uplink
or downlink slot in 3GPP LTE.
[0064] Referring to FIG. 4, the uplink slot includes a plurality of
OFDM (orthogonal frequency division multiplexing) symbols in the
time domain and NRB resource blocks (RBs) in the frequency domain.
For example, in the LTE system, the number of resource blocks
(RBs), i.e., NRB, may be one from 6 to 110.
[0065] The resource block is a unit of resource allocation and
includes a plurality of sub-carriers in the frequency domain. For
example, if one slot includes seven OFDM symbols in the time domain
and the resource block includes 12 sub-carriers in the frequency
domain, one resource block may include 7.times.12 resource elements
(REs).
[0066] Meanwhile, the number of sub-carriers in one OFDM symbol may
be one of 128, 256, 512, 1024, 1536, and 2048.
[0067] In 3GPP LTE, the resource grid for one uplink slot shown in
FIG. 4 may also apply to the resource grid for the downlink
slot.
[0068] The physical channels in 3GPP LTE may be classified into
data channels such as PDSCH (physical downlink shared channel) and
PUSCH (physical uplink shared channel) and control channels such as
PDCCH (physical downlink control channel), PCFICH (physical control
format indicator channel), PHICH (physical hybrid-ARQ indicator
channel) and PUCCH (physical uplink control channel).
[0069] The uplink channels include a PUSCH, a PUCCH, an SRS
(Sounding Reference Signal), and a PRACH (physical random access
channel).
[0070] FIG. 5 is a flowchart illustrating a random access procedure
in 3GPP LTE.
[0071] The random access procedure is used for the UE 10 to achieve
UL synchronization with the base station, that is, eNodeB 20, or
for UE to receive UL radio resource assignment from the base
station.
[0072] The UE 10 receives a root index and a physical random access
channel (PRACH) configuration index from the eNodeB 20. Each cell
has 64 candidate random access preambles defined by a ZC
(Zadoff-Chu) sequence. The root index refers to a logical index
used for the UE to generate the 64 candidate random access
preambles.
[0073] The transmission of random access preambles is limited to
specific time and frequency resources for each cell. The PRACH
configuration index indicates a specific subframe available for
transmission of the random access preamble and a preamble
format.
[0074] The UE 10 transmits an arbitrarily selected random access
preamble to the eNodeB 20. In this connection, the UE 10 selects
one of the 64 candidate random access preambles. Further, the UE 10
selects a subframe corresponding to the PRACH configuration index.
The UE 10 transmits the selected random access preamble on the
selected subframe.
[0075] Upon receiving the random access preamble, the eNodeB 20
sends a random access response (RAR) to the UE 10. The random
access response is detected using two steps as follows. First, the
UE 10 detects a PDCCH masked using a random access-RNTI (R-RNTI).
Then, the UE 10 receives the random access response in a MAC
(Medium Access Control) PDU (Protocol Data Unit) on a PDSCH
indicated by the detected PDCCH.
[0076] <Carrier Aggregation>
[0077] A carrier aggregation system is now described.
[0078] A carrier aggregation system aggregates a plurality of
component carriers (CCs). A meaning of an existing cell is changed
according to the above carrier aggregation. According to the
carrier aggregation, a cell may signify a combination of a downlink
component carrier and an uplink component carrier or an independent
downlink component carrier.
[0079] Further, the cell in the carrier aggregation may be
classified into a primary cell, a secondary cell, and a serving
cell. The primary cell signifies a cell operated in a primary
frequency. The primary cell signifies a cell which UE performs an
initial connection establishment procedure or a connection
reestablishment procedure or a cell indicated as a primary cell in
a handover procedure. The secondary cell signifies a cell operating
in a secondary frequency. Once the RRC connection is established,
the secondary cell is used to provided an additional radio
resource.
[0080] As described above, the carrier aggregation system may
support a plurality of component carriers (CCs), that is, a
plurality of serving cells unlike a single carrier system.
[0081] The carrier aggregation system may support a cross-carrier
scheduling. The cross-carrier scheduling is a scheduling method
capable of performing resource allocation of a PDSCH transmitted
through other component carrier through a PDCCH transmitted through
a specific component carrier and/or resource allocation of a PUSCH
transmitted through other component carrier different from a
component carrier basically linked with the specific component
carrier.
[0082] <IoT (Internet of Things) Communication>
[0083] Hereinafter, the IoT communication will be described.
[0084] FIG. 6A shows an example of IoT (Internet of Things)
communication.
[0085] The IoT communication refers to the exchange of information
between the IoT devices 100 without human interaction through the
base station 200 or between the IoT device 100 and the server 700
through the base station 200. In this way, the IoT communication is
also referred to as CIoT (Cellular Internet of Things) in that the
IoT communication is performed through the cellular base
station.
[0086] This IoT communication may refer to a kind of machine type
communication (MTC). Therefore, the IoT device may be referred to
as an MTC device.
[0087] The IoT service is differentiated from the conventional
communication service in which a person is involved. The IoT
service may include various categories of services, including
tracking, metering, payment, medical services, and remote controls.
For example, the IoT services may include meter reading, water
level measurement, surveillance camera utilization, vending machine
related inventory reporting, and so on.
[0088] The IoT communication has a small amount of transmitted
data. Further, uplink or downlink data transmission/reception
rarely occurs. Accordingly, it is desirable to lower a price of the
IoT device 100 and reduce battery consumption in accordance with
the low data rate. In addition, since the IoT device 100 has low
mobility, the IoT device 100 has substantially the unchanged
channel environment.
[0089] FIG. 6B is an example of a cell coverage extension or
enhancement for the IoT device.
[0090] Recently, it is considered to extend or enhance the cell
coverage of the base station for the IoT device 100. To this end,
various techniques for cell coverage extension or enhancement are
discussed.
[0091] However, if the coverage of the cell is extended or
enhanced, and when the base station transmits the downlink channel
to the IoT device located in the coverage extension (CE) or
coverage enhancement (CE) region, the IoT device has difficulty in
receiving the downlink channel. Similarly, when the IoT device
located in the CE region transmits the uplink channel to the base
station as the channel is, the base station has difficulty in
receiving the uplink channel.
[0092] In order to solve this problem, the downlink channel or
uplink channel may be repeatedly transmitted on a plurality of
subframes. The transmission of uplink/downlink channels repeatedly
on the plurality of subframes is referred to as bundle
transmission.
[0093] Thus, the IoT device or base station may receive the bundle
of downlink/uplink channels on the plurality of subframes, and may
decode a part or all of the bundle. As a result, the decoding
success rate can be increased.
[0094] FIG. 7A and FIG. 7B are views illustrating examples of a
sub-band in which the IoT device operates.
[0095] In one approach to a low cost of the IoT device, as shown in
FIG. 7A, the IoT device may use, for example, a sub-band of
approximately 1.4 MHz regardless of a system bandwidth of the
cell.
[0096] In this connection, the region of the sub-band in which the
IoT device operates may be located in a central region (e.g., six
middle PRBs) of the system bandwidth of the cell, as shown in FIG.
7A.
[0097] Alternatively, as shown in FIG. 7B, in order to multiplex
the IoT devices in one subframe, a plurality of sub-bands for the
IoT devices are allocated in one subframe, so that different
sub-bands may be used by different IoT devices. In this connection,
most of the IoT devices may use sub-bands other than the sub-bands
in the central region (e.g., the middle six PRBs) of the system
band of the cell.
[0098] The IoT communication operating on such a reduced bandwidth
may be called NB (Narrow Band) IoT communication or NB CIoT
communication.
[0099] FIG. 8 shows an example of a time resource used for the
NB-IoT communication on M-frames basis.
[0100] Referring to FIG. 8, a frame that may be used for NB-IoT
communication may be referred to as an M-frame, and the length of
the M-frame may be illustratively 60 ms. Further, a subframe that
may be used for the NB IoT communication may be referred to as an
M-subframe, and its length may be exemplarily 6 ms. Thus, the
M-frame may include ten M-subframes.
[0101] Each M-subframe may include two slots, and each slot may be
illustratively 3 ms in length.
[0102] However, unlike what is shown in FIG. 8, a slot that may be
used for the NB IoT communication may have a length of 2 ms. In
this case, the subframe may have a length of 4 ms and the frame may
have a length of 40 ms. Such a case will be described in more
detail with reference to FIG. 9.
[0103] FIG. 9 is another example of a time resource and a frequency
resource that may be used for the NB IoT communication.
[0104] Referring FIG. 9, a physical channel or a physical signal
transmitted on one slot in the uplink of the NB-IoT communication
includes N.sub.symb.sup.UL SC-FDMA symbols in the time domain, and
N.sub.sc.sup.UL subcarriers in the frequency domain. The uplink
physical channel may be divided into an NPUSCH (Narrowband Physical
Uplink Shared Channel) and an NPRACH (Narrowband Physical Random
Access Channel). Further, in the NB-IoT communication, the physical
signal may be NDMRS (Narrowband DeModulation Reference Signal).
[0105] In the NB-IoT communication, during the T.sub.slot slot, the
uplink bandwidth of the N.sub.sc.sup.UL subcarriers is as
follows.
TABLE-US-00003 TABLE 3 Subcarrier spacing N.sub.sc.sup.UL
T.sub.slot .DELTA.f = 3.75 kHz 48 61440 * T.sub.s .DELTA.f = 15 kHz
12 15360 * T.sub.s
[0106] In the NB-IoT communication, each resource element (RE) of a
resource grid nay be defined using an index pair (k, l)
respectively indicating a time region and a frequency region in the
corresponding slot. In this connection, k=0, . . . ,
N.sub.sc.sup.UL-1, and 1=0, . . . , N.sub.symb.sup.UL-1.
[0107] In the NB-IoT communication, a resource unit (RU) is used to
map the NPUSCH to the resource element (RE). The resource units
(RU) may be defined as successive subcarriers N.sub.sc.sup.RU, and
successive SC-FDMA symbols N.sub.symb.sup.UL
N.sub.slots.sup.UL.
[0108] In this connection, N.sub.sc.sup.RU, N.sub.symb.sup.UL and
N.sub.slots.sup.UL may be as follows:
TABLE-US-00004 TABLE 4 NPUSCH format .DELTA.f N.sub.sc.sup.RU
N.sub.slots.sup.UL N.sub.symb.sup.UL 1 3.75 kHz 1 16 7 15 kHz 1 16
3 8 6 4 12 2 2 3.75 kHz 1 4 15 kHz 1 4
[0109] In the above table, NPUSCH format 1 is used to transmit the
uplink data channel. Further, NPUSCH format 2 is used to transmit
uplink control information.
[0110] Symbols of a symbol block z(0), . . . ,
z(M.sub.symb.sup.sp-1) are multiplied by an amplitude scaling
factor based on a transmission power PNPUSCH. Then, the multiplied
symbols z(0), . . . , z(M.sub.symb.sup.ap-1) are mapped
sequentially from z(0) to z(M.sub.symb.sup.ap-1) to subcarriers
allocated for transmission of the NPUSCH. The mapping for the
resource element (k, l) starts at a first slot in an assigned
resource unit (RU). Then, the resource element (k, l) is mapped in
an increasing order from an index k to an index l. The NPUSCH may
be mapped to one or more resource units (RUs).
Disclosure of Present Specification
[0111] In the present specification, a device that operates on a
reduced bandwidth according to
low-complexity/low-capability/low-specification/low-cost is
hereinafter referred to as an LC device, a bandwidth-reduced (BL)
device, or an NB-IoT device. Here, according to the disclosure of
the present specification, coverage extension/enhancement (CE) may
be divided into two modes. A first mode (also referred to as CE
mode A) is a mode in which repeated transmission is not performed
or a small number of repeated transmissions are allowed. A second
mode (also referred to as CE mode B) is a mode in which a large
number of repeated transmissions are allowed. An NB-IoT device (LC
device or BL device) can be signaled as to which mode to operate in
of these two modes. Here, different parameters may be considered by
the NB-IoT device for transmission/reception of a control
channel/data channel depending on the CE mode. Also, a DCI format
monitored by the NB-IoT device may vary depending on the CE mode.
However, some physical channels may be repeatedly transmitted the
same number of times regardless of CE mode A and CE mode B.
[0112] The NB-IoT device may perform communication in an area with
a poor channel environment (e.g., under a bridge, under the sea, or
on the sea) and thus can use repeated transmission or power
boosting techniques. Power boosting may be a method in which a
frequency domain is reduced and power is concentrated on a
particular frequency resource. For example, when one RB includes 12
REs, transmission may be performed by concentrating power on a
particular RE in a particular RB, instead of through a plurality of
RBs.
[0113] A method of performing communication by concentrating power
on one RE in a RB may be collectively referred to as a single-tone
transmission method.
[0114] However, the single-tone transmission method is not
currently supported by the 3GPP standard. In particular, according
to the current 3GPP standard, a random access preamble for initial
access is designed to be transmitted through one RB, that is, 12
subcarriers.
[0115] Thus, the present specification is disclosed to improve a
PRACH, specifically a random access preamble, in order to perform a
random access procedure by a single-tone transmission method.
[0116] Hereinafter, the present specification will be described
with reference to a PRACH, that is, a random access preamble, but
the idea of the invention disclosed in the present specification
can also be applied to other uplink channels. In addition, although
the present specification illustrates a single-tone transmission
method, the idea of the invention disclosed in the present
specification can be extended to a multi-tone transmission
method.
[0117] For the convenience of description, it is assumed in the
present specification that a BS has a cell coverage radius of 35
km. For the convenience of description, it is assumed in the
present specification that a subcarrier spacing is 15 kHz or 3.75
kHz.
I. First Embodiment: Design of Frequency Resource Unit for
Transmission of PRACH Signal (e.g., Random Access Preamble)
[0118] When a wireless device transmits a PRACH at a plurality of
frequencies by a single-tone transmission method, a BS may estimate
the arrival time. For example, it is assumed that, defining a PRACH
signal (e.g., a random access preamble) as x(t), the wireless
device transmits X[0] at frequency f1 in a first time period and
transmits X[1] at frequency f2 in a second time period. Here, it is
assumed that frequencies f1 and f2 are spaced apart from each other
by a predetermined frequency offset. Then, the BS can measure the
arrival time, robustly against a frequency error, using the
frequency offset. Specifically, when the reciprocal number of a
subcarrier spacing is denoted by T, arrival time is denoted by
.DELTA.t, and a frequency is denoted by .DELTA.f, a value mapped to
an RE corresponding to frequency f1 is
X[0]*exp(-j2n{f1+.DELTA.f)/T}.DELTA.t) and a value mapped to an RE
corresponding to frequency f2 is
X[1]*exp(-j2.pi.{f2+.DELTA.f)/T}.DELTA.t). By conjugate
multiplication using the values of these two REs,
X[0]*X[1]*exp(-j2.pi.{f2-f1)/T}.DELTA.t) can be derived, by which
the arrival time can be calculated. However, a range in which the
arrival time can be measured may be limited to up to T (limited to
a case where the difference between f2 and f1 is 1).
[0119] The foregoing transmission of the PRACH signal (e.g., random
access preamble) in the two time periods may be extended to a
plurality of time periods (e.g., 100 times). Further, the number of
frequency intervals may also be plural. However, considering
overheads, two frequency intervals may be effective. A time period
for continuously transmitting a PRACH signal (e.g., a random access
preamble) on the same frequency resource may be referred to as a
PRACH symbol, and a unit for a PRACH signal (e.g., a random access
preamble) transmitted in a corresponding region may be referred to
as a frequency resource unit. A specific example of a frequency
resource unit for transmission of a PRACH signal (e.g., a random
access preamble) is illustrated below, which will be described with
reference to FIGS. 10A to 10D.
[0120] FIGS. 10A and 10B illustrate a first example of the first
embodiment of the present specification. FIG. 10C illustrates a
second example, and FIG. 10D illustrates a third example.
[0121] In the first example, it is assumed that the subcarrier
spacing is 3.75 kHz. Here, a frequency resource unit for
transmission of a PRACH signal (e.g., a random access preamble) may
include six sub-symbols. One sub-symbol is used as a CP. When a BS
has a cell coverage radius of 35 km, the round-trip time (RTT) may
be 233.33 s and the maximum delay spread may be 16.67 .mu.s.
Therefore, as illustrated in FIGS. 10A and 10B, it is proposed in
the first example to design a CP to have a length of 266.67 .mu.s.
As illustrated in FIG. 10A, when the number of sub-symbols included
in the frequency resource unit for transmission of the PRACH signal
(e.g., a random access preamble) is six, the frequency resource
unit for transmission of the PRACH signal (e.g., a random access
preamble) may be 1.6 ms. As illustrated in FIG. 10B, when the
number of sub-symbols is three, the frequency resource unit may be
0.8 ms. Further, when the number of sub-symbols is 15, the
frequency resource unit may be 4 ms.
[0122] In the second example, it is assumed that the subcarrier
spacing is 15 kHz. Here, a frequency resource unit for transmission
of a PRACH signal (e.g., a random access preamble) may include 15
sub-symbols. Four sub-symbols are used as a CP. Referring to FIG.
10C, it is proposed in the second example to set the length of the
CP to 266.67 .mu.s. Depending on a value mapped to each sub-symbol,
the desired coverage radius of a BS may be supported. When the same
value is mapped to the respective sub-symbols, an arrival time of
only up to 66.67 s can be measured and distinguished. Unlike in
FIG. 10C, the number of sub-symbols included in the frequency
resource unit for transmission of the PRACH signal (e.g., a random
access preamble) may be 12 or 24. When the number of sub-symbols is
12, the frequency resource unit for transmission of the PRACH
signal (e.g., a random access preamble) may have a length of 0.8
ms. When the number of sub-symbols is 24, the frequency resource
unit for transmission of the PRACH signal (e.g., a random access
preamble) may have a length of 1.6 ms.
[0123] In the third example, it is assumed that the subcarrier
spacing is 15 kHz, and a frequency resource unit for transmission
of a PRACH signal (e.g., a random access preamble) may include 30
sub-symbols. Here, six sub-symbols are used as a CP. Referring to
FIG. 10D, it is proposed in the third example to set the length of
the CP to 400 .mu.s. Depending on a value mapped to each
sub-symbol, the desired coverage radius of a BS may be supported.
When the same value is mapped to the respective sub-symbols, an
arrival time of only up to 66.67 .mu.s can be measured and
distinguished. Unlike in FIG. 10D, the number of sub-symbols
included in the frequency resource unit for transmission of the
PRACH signal (e.g., a random access preamble) may be 12 or 24. When
the number of sub-symbols is 12, the frequency resource unit for
transmission of the PRACH signal (e.g., a random access preamble)
may have a length of 0.8 ms. When the number of sub-symbols is 24,
the frequency resource unit for transmission of the PRACH signal
(e.g., a random access preamble) may have a length of 1.6 ms.
[0124] A symbol which is a frequency resource unit for transmission
of a PRACH signal (e.g., a random access preamble) may be subjected
to frequency hopping, which will be described with reference to
FIG. 11.
[0125] FIG. 11 illustrates an example of transmission of a symbol
which is a frequency resource unit for transmission of a PRACH
signal (e.g., a random access preamble).
[0126] As illustrated in FIG. 11, a symbol which is a frequency
resource unit for transmission of a PRACH signal (e.g., a random
access preamble) may be subjected to frequency hopping. In this
case, the same value may be set to be mapped to each sub-symbol in
view of PAPR, and a different value may be mapped for each
frequency resource unit. When a plurality of units forms one PRACH
signal (e.g., a random access preamble), values transmitted for
individual frequency resource units may be expressed in a sequence
form. For example, when 100 units form a PRACH signal (e.g., a
random access preamble), one value in a sequence having a length of
100 may be considered to be transmitted in each unit. A frequency
at which a unit is transmitted at each time may be changed, and
hopping between two or more regions in a particular pattern may be
considered.
[0127] I-1. Addition of Guard Time (GT)
[0128] For the foregoing frequency resource unit, considering
coexistence with another transport channel (e.g., PUCCH/PUSCH), it
may be considered to add a guard time (GT) after transmission of a
sequence. The GT period is based on a symbol number, that is, a
multiple of T, and may be set to 233.33 s or longer. Alternatively,
the GT period is based on a symbol number, that is, a multiple of
T, and may be set such that a frequency resource unit for
transmission of a PRACH signal (e.g., a random access preamble)
ends with a multiple of 1 ms (relative to a subcarrier spacing of
15 kHz) in order to match the boundary of a subframe for another
physical channel. Specifically, among a plurality of frequency
resource units for all PRACH transmissions, only a particular unit
may have a GT. The particular unit may be the last unit among those
for PRACH transmission.
[0129] When a GT is not employed, it may be considered to allocate
a dedicated frequency resource for a PRACH signal (e.g., a random
access preamble). Specifically, the frequency resource may be
reported to a wireless device via a higher-layer signal (e.g., an
RRC signal) or SIB. Transmission of other physical channels, such
as PUCCH and PUSCH, is restricted in the corresponding region.
[0130] I-2. Time-Domain Transmission Unit for PRACH Signal (e.g.,
Random Access Preamble)
[0131] In the single-tone transmission method, a basic PRACH
transmission unit may be set to be longer than a subframe for other
transport channels, in which case a plurality of PRACH resources
may be allocated for a single or a plurality of subframe groups.
Basically, a PRACH resource may be transmitted on the boundary of a
subframe or a slot and may include a first part or a last part of a
subframe boundary. Alternatively, a form in which a subframe
boundary is not aligned with the start or end position of a PRACH
resource may be considered in order to maximize a PRACH resource
included in a particular subframe or subframe group. Specifically,
the resource may be used only for PRACH repetition. The foregoing
description is merely an example and may be extended to a
multi-tone transmission method.
[0132] FIGS. 12A to 12C illustrate examples in which a time
resource unit for a PRACH signal (e.g., a random access preamble)
is 1.3 ms when a subframe has a length of 1 ms and when a subframe
has a length of 4 ms.
[0133] Referring to FIG. 12A, where a subframe has a length of 1
ms, a first time resource with a length of 1.3 ms for a PRACH
signal (e.g., a random access preamble) is allocated to be aligned
with the start boundary of a first subframe, and a second time
resource with a length of 1.3 ms is allocated to the end boundary
of a third subframe. Referring to FIG. 12B, where a subframe has a
length of 4 ms, a first time resource with a length of 1.3 ms for a
PRACH signal (e.g., a random access preamble) is allocated to be
aligned with the start boundary of a subframe, and a second time
resource is allocated to be aligned with a point 1 ms away from the
end of the subframe.
[0134] Further, referring to FIG. 12B, where a subframe has a
length of 1 ms, a first time resource with a length of 1.3 ms is
allocated to be aligned with the start boundary of a first
subframe, and a third time resource with a length of 1.3 ms is
allocated to the end boundary of a fourth subframe. A second time
resource with a length of 1.3 ms is allocated such that the center
thereof is aligned with the boundary between second and third
subframes. Referring to FIG. 12B, where a subframe has a length of
4 ms, a first time resource with a length of 1.3 ms is allocated to
be aligned with the start boundary of a subframe, and a third time
resource with a length of 1.3 ms is allocated to be aligned with
the end boundary of the subframe. A second time resource with a
length of 1.3 ms is allocated such that the center thereof is
aligned with the center of the 4 ms subframe.
[0135] Referring to FIG. 12C, where a subframe has a length of 1
ms, a first time resource with a length of 1.3 ms is allocated to
be aligned with the start boundary of a first subframe, and a third
time resource with a length of 1.3 ms is allocated to be aligned
with the end boundary of a fourth subframe. Referring to FIG. 12C,
where a subframe has a length of 4 ms, a first time resource with a
length of 1.3 ms is allocated to be aligned with the start boundary
of a subframe, and a second time resource with a length of 1.3 ms
is allocated to be aligned with the end boundary of the
subframe.
[0136] I-3. TDD Environment
[0137] It is necessary to consider interference that is received
from or is given to a TDD system when a PRACH for NB-IoT is
transmitted in the TDD system or a TDD system depending on the
environment of a neighboring cell. In this case, it is needed to
set a PRACH resource only in a UL region in accordance with a
particular TDD UL-DL configuration. A simple method may be
considered in which a time-domain transmission unit for a PRACH
signal (e.g., a random access preamble) is designed to be 1 ms or
shorter and is allocated to a UL region. Generally, as the number
of symbols forming a time-domain transmission resource increases, a
sequence can be repeated or the length of a sequence can be
extended, which can improve the performance of a BS detecting a
PRACH signal (e.g., a random access preamble). Therefore, it is
considered to change the length of a time-domain transmission unit
for a PRACH signal (e.g., a random access preamble) or to change
the number of symbols forming the time-domain transmission unit
depending on the number of available UL subframes or a UL region
(e.g., a symbol unit). The UL region may be a plurality of
consecutive UL subframes set according to a TDD UL-DL configuration
or may be a corresponding time period. In addition, it is
considered to also include a time period corresponding to UpPts in
a time-domain transmission resource for a PRACH signal (e.g., a
random access preamble) depending on a special subframe
configuration. The time-domain transmission resources for the PRACH
signal (e.g., a random access preamble) generated by the above
methods may be set in different PRACH formats. Alternatively, a
time-domain transmission resource for a PRACH signal (e.g., a
random access preamble) may be set on the basis of a parameter
signaled via a higher-layer signal. Alternatively, a time-domain
transmission resource for a PRACH signal (e.g., a random access
preamble) may be preset according to the TDD UL-DL configuration
and/or the special subframe configuration.
[0138] A specific example of defining a time-domain transmission
resource for a PRACH signal (e.g., a random access preamble)
according to the TDD UL-DL configuration is illustrated below.
Hereinafter, for the convenience of description, it is assumed that
a subcarrier spacing for a PRACH signal (e.g., a random access
preamble) is 3.75 kHz. However, even though the subcarrier spacing
is changed, when the number of symbols is suitably changed
according to the UL time period described below, the following
description may be applied. When a time period and a time-domain
transmission resource for a PRACH signal (e.g., a random access
preamble) do not correspond to each other in length, (1) the
time-domain transmission resource for the PRACH signal (e.g., a
random access preamble) may be aligned with the start or end
boundary of a UL time period including UpPts, or (2) the
time-domain transmission resource for the PRACH signal (e.g., a
random access preamble) may be aligned with the start or end
boundary of consecutive UL subframe groups excluding UpPts.
First Example: Three UL Subframes+0/1/2 UL Symbols
[0139] According to the first example, a time-domain transmission
resource for a PRACH signal (e.g., a random access preamble) may be
represented by a time period of 3 ms, 3.667 ms, 4.333 ms, or the
like. In TDD UL-DL configuration #0, the time-domain transmission
resource may be the entire period of a radio frame. In TDD UL-DL
configurations #3 and #6, the time-domain transmission resource may
be the first half period of a radio frame. When a subcarrier
spacing is 3.75 kHz, the time-domain transmission resource may be 9
or 11, 12 or 13, or 15 or 16 symbols. To set the time-domain
transmission resource for the PRACH signal (e.g., a random access
preamble) in ms, 9 (2.4 ms), 12 (3.2 ms) and 15 (4 ms) symbols may
be set. Here, a CP may be one symbol.
Second Example: Two UL Subframes+0/1/2 UL Symbols
[0140] According to the second example, a time-domain transmission
resource for a PRACH signal (e.g., a random access preamble) may be
represented by a time period of 2 ms, 2.667 ms, 3.333 ms, or the
like. In TDD UL-DL configuration #1, the time-domain transmission
resource may be the entire period of a radio frame. In TDD UL-DL
configuration #4, the time-domain transmission resource may be the
first half period of a radio frame. In TDD UL-DL configuration #6,
the time-domain transmission resource may be the last half period
of a radio frame.
Third Example: One UL Subframes+0/1/2 UL Symbols
[0141] According to the third example, a time-domain transmission
resource for a PRACH signal (e.g., a random access preamble) may be
represented by a time period of 1 ms, 1.667 ms, 2.333 ms, or the
like. In TDD UL-DL configuration #2, the time-domain transmission
resource may be the entire period of a radio frame. In TDD UL-DL
configuration #5, the time-domain transmission resource may be the
first half period of a radio frame.
II. Second Embodiment: Method for Mapping Data/Sequence in
Frequency Resource Unit for Transmission of PRACH Signal (e.g.,
Random Access Preamble)
[0142] When a subcarrier spacing is not set to be sufficiently
short, compared to the desired cell coverage radius of a BS, the
arrival time of a PRACH signal (e.g., a random access preamble)
that the BS can distinguish is reduced. Thus, the foregoing method
of mapping the same value to all sub-symbols in a time transmission
resource may not be suitable. Therefore, in order to efficiently
estimate the arrival time of a PRACH signal (e.g., a random access
preamble), it is necessary to design a different value or sequence
to be mapped to a sub-symbol. Generally, since NB-IoT devices are
manufactured with low performance in order to reduce complexity, it
is necessary to maximally reduce PAPR. Thus, it may be advantageous
to maintain a small variation in value between sub-symbols in a
time-domain transmission resource for a PRACH signal (e.g., a
random access preamble). A specific example of a method for mapping
a value to a sub-symbol in a time-domain resource for a PRACH
signal (e.g., a random access preamble) is illustrated below.
[0143] FIG. 13A illustrates a first example of the second
embodiment of the present specification. FIG. 13B illustrates a
third example.
[0144] For the convenience of description, the number of
sub-symbols in a time-domain resource for a PRACH signal (e.g., a
random access preamble) is denoted by Nseq, the number of
sub-symbols for a CP is denoted by Ncp, and the number of
time-domain resource units for transmitting a PRACH signal (for
example, a the preamble is transmitted is den random access
preamble) is denoted by M.
[0145] In the first example, a wireless device first generates a
sequence with a length of (Nseq-Ncp)*M. That is, as illustrated in
FIG. 13A, when M=4, the wireless device generates a sequence with a
length of (Nseq-Ncp)*4 and divides the sequence to be allocated to
four time-domain resources. The sequence may be a Zha-doff Chu (ZC)
sequence. In order to have a length of a prime number, the ZC
sequence may be obtained by generating a sequence to be longer than
(Nseq-Ncp)*M and cutting off a portion or by generating a sequence
to be shorter than (Nseq-Ncp)*M and circularly repeating the
sequence. A plurality of sequences may be generated by adding root
index, or a different sequence may be generated using a cyclic
shift in the same root index.
[0146] Alternatively, a sequence with a length of (Nseq-Ncp)*M' may
be generated, where M' is smaller than the number of time-domain
resource units for transmitting a PRACH signal (e.g., a random
access preamble). M' may be a preset value or a value signaled
through a higher-layer signal or a system information block
(SIB).
[0147] In a second example, the wireless device generates a
sequence with a length of Nseq*M. The sequence may be a sequence
for Decrete Fourier Transform (DFT). The DFT sequence may be
exp(j2pi*k*p/((Nseq-Ncp)*M)), where k=0, 1, . . . , (Nseq-Ncp)*M-1.
The value of p may be adjusted to generate an additional sequence.
The value of p may be limited in view of PAPR. For example, the
value of p may include at least 1 and (Nseq-Ncp)*M-1.
[0148] In the third example, the wireless device generates a
sequence with a length of (Nseq-Ncp) for each time-domain resource
unit. That is, as illustrated in FIG. 13B, when M is 4, the
wireless device generates four sequences with a length of
(Nseq-Ncp). The sequence may be a ZC sequence or a DFT sequence.
The same sequence may be mapped to all of individual time-domain
resource units or a different sequence may be generated for each
time-domain resource unit. It may be considered to generate at
least two types of sequences in view of improvement in
autocorrelation performance and complexity. For example, a first
sequence may be used for a first tone, and a second sequence may be
used for a second tone.
[0149] In the above examples, a sub-symbol in each time-domain
resource unit includes a sequence with a length of (Nseq-Ncp) and a
CP generated by copying the last part of the sequence.
[0150] Although the sequence has been illustrated as a ZC sequence
or a DFT sequence, other sequences may be applied.
[0151] When there is a plurality of sequences for a PRACH signal
(e.g., a random access preamble) configured with a plurality of
time-domain resource units (e.g., a smaller number of sequences
than M are generated and distributed in the first example or a
sequence is generated for each time-domain resource unit in the
third example), it may be considered to additionally introduce an
orthogonal cover code (OCC) in order to increase multiplexing
capacity. For example, when the number of time-domain resource
units is M, an OCC with a length of M may be generated, and an OCC
configuration value may be multiplied with a symbol value in each
time-domain resource unit for each time-domain resource unit.
Alternatively, M/M `OCCs with a length of M`, which is smaller than
M, may be generated, and an OCC with a length of M may be applied
to each symbol value in M' time-domain resource units. Then, a BS
can distinguish a plurality of PRACHs by a combination of a
sequence and an OCC. More specifically, for multiplexing, a root
index and/or cyclic shift and/or OCC for a sequence may be changed.
In a case of using a plurality of ZC sequences, it may be
considered to set a different cyclic shift for each ZC
sequence.
[0152] When the same value is mapped in the same time-domain
resource unit, it may be necessary to generate a sequence with a
length of M in view of all PRACH signals (e.g., random access
preambles).
III. Third Embodiment: Methods for Frequency Hopping Between
Frequency Resource Units and Resource Mapping for Transmission of
PRACH Signal (e.g., Random Access Preamble)
[0153] The accuracy with which a BS estimates the arrival time of a
received PRACH may vary depending on a frequency region occupied
for PRACH transmission. For example, as the frequency region
occupied for the PRACH transmission is wider, the result of
performing an autocorrelation function becomes sharper. That is, a
correlation value is sharply different depending on whether timing
is right or not. Therefore, an error range may be reduced when
estimating the arrival time. For the foregoing method, it may be
considered to perform frequency hopping when mapping a PRACH signal
(e.g., a random access preamble) according to the single-tone
transmission method to a frequency resource unit. However,
depending on a method of designing a frequency resource unit, the
maximum estimable arrival time range may be reduced as the value
increases according to the difference between the frequencies to
which a frequency resource unit is mapped (in section I, the
estimable range can be expressed as T/(f2-f1)). Therefore, in a
next-generation system, it is possible to introduce a plurality of
times of frequency hopping for a PRACH signal (e.g., a random
access preamble) according to the single-tone transmission method.
Further, a frequency change range may be varied when performing
each time of hopping. For example, a first range may have two
frequency regions to be adjacent, while a second range may have two
frequency regions to be as far away as possible.
[0154] In mapping a PRACH signal (e.g., a random access preamble)
according to the single-tone transmission method to a
time-frequency resource unit, when a sequence of a random access
preamble is generated and/or resource mapping is performed in view
of interference between a plurality of cells, inter-cell
randomization may be required. For example, for the sequence of the
random access preamble, (1) a wireless device may consider
generating a single random access preamble or a plurality of random
access preambles to be different for each cell using a physical
cell ID, identification information on a cell performing an NB-IoT
operation, or a seed value signaled through a higher-layer signal.
Alternatively, (2) a network may adjust the sequence of the random
access preamble or the set of the sequence to be set differently
for each cell. Then, each cell may notify wireless devices of the
sequence set of the random access preamble through system
information, e.g., an SIB. Here, each cell may transmit a
cell-specific offset used for frequency hopping or an initial
offset value to the wireless devices. Such transmission may be
performed through system information, e.g., an SIB.
[0155] In a resource mapping method, the randomization effect may
be considered to be reduced when the same pattern is used for each
cell. The effect of randomizing inter-cell interference may be
expected by avoiding PRACH signals (e.g., random access preambles)
according to the single-tone transmission method from colliding
between cells, and by allowing only some of the PRACH signals
(e.g., random access preambles) to collide if it is difficult for
all the PRACH signals to avoid collision. To this end, a frequency
hopping method or a resource mapping method for a PRACH signal
(e.g., a random access preamble) according to the single-tone
transmission method may be set independently for each cell. In the
methods, (1) a wireless device may generate a single frequency
hopping pattern or resource mapping pattern or a plurality of
frequency hopping patterns or resource mapping patterns for each
cell using a physical cell ID, identification information on a cell
performing an NB-IoT operation, or a seed value signaled through a
higher-layer signal. Alternatively, (2) a network may adjust
information on a frequency hopping pattern or a resource mapping
pattern (which may be pattern information itself or a parameter
used to generate a pattern) to be used for each cell between cells
and may transmit the information to a wireless device. Such
transmission may be performed through system information, e.g., an
SIB.
[0156] A unit for performing frequency hopping may be (1) a unit
for transmitting a PRACH signal (e.g., a random access preamble)
mapped according to the single-tone transmission method.
Alternatively, to achieve the desired cell coverage radius of a BS,
a unit for performing frequency hopping may be (2) a group of a
plurality of transmission units mapped by a specific frequency
difference. Specifically, the group of the plurality of
transmission units may be a group of two consecutive transmission
units adjacent to each other on the frequency axis. Alternatively,
a unit for performing frequency hopping may be a group of a
plurality of subcarrier indexes. For example, a unit for performing
frequency hopping may be a group of subcarriers corresponding to
{0, 1, 6, 7} from a reference subcarrier index. Alternatively, to
secure the length of a sequence of a random access preamble, a unit
for performing frequency hopping may be (3) a plurality of
transmission units mapped to the same frequency. Particularly, in a
frequency-selective channel, a sudden frequency change between
transmission units by frequency hopping may dilute sequence
characteristics of a random access preamble or may act as an
obstacle to detection performance. In addition, when a PRACH signal
(e.g., a random access preamble) is repeatedly transmitted, the
PRACH may be randomized on the time axis in addition to hopping
between frequencies for inter-cell randomization. In this case, (4)
the time at which frequency hopping is performed may be changed
over time on the basis of a pseudo random sequence. The sequence
may be generated on the basis of a physical cell ID, identification
information on a cell performing an NB-IoT operation, or a seed
value signaled through a higher-layer signal.
[0157] Meanwhile, a unit for performing hopping may be
independently set according to the coverage extension (CE) level.
Alternatively, when a unit for performing hopping is preset, the
number of transmission units for a PRACH signal (e.g., a random
access preamble) may be designated according to a coverage
extension level or a repetition number for a PRACH signal (e.g., a
random access preamble) or a method for configuring a unit for
performing hopping (e.g., by how many transmission units hopping is
performed) may be set for each coverage extension level through a
higher-layer signal.
[0158] A frequency region for performing frequency hopping may be
(1) the entire frequency region (single narrow band or a plurality
of narrow bands) in which NB-IoT operates. Alternatively, a
frequency region for performing frequency hopping may be limited to
(2) a frequency region set through a higher-layer signal. By
limiting the frequency region, PUCCH/PUSCH transmission for other
wireless devices may be allowed in the same NB-IoT band
(narrowband). Specifically, a frequency region for transmitting a
PRACH may be set differently according to the coverage extension
level.
[0159] Specific examples of a frequency hopping pattern will be
described below.
[0160] In a first example, frequency hopping is performed between
hopping units by a bandwidth set in advance or through a
higher-layer signal in a particular frequency region. A frequency
change range may be limited within a particular time period. Thus,
it may be considered to apply a sequence of a random access
preamble with a certain length or longer to a PRACH according to
the single-tone transmission method. Specifically, for example,
when the transmission of a PRACH signal (e.g., a random access
preamble) according to the single-tone transmission method is
started with a frequency position f set to f1, a frequency position
f at the next timing may be hopped in the form of f+delta or
f-delta on the basis of the previous frequency position f.
[0161] In a second example, resource mapping for a hopping unit is
performed with respect to a plurality of frequencies set in advance
or through a higher-layer signal in a particular frequency
region.
[0162] In a third example, frequency hopping between hopping units
is performed in a particular pattern within a particular frequency
region. The pattern may be a pseudo random sequence that is set
using a transmission time (e.g., a subframe index or a symbol
index) and/or a physical cell ID and/or a hopping seed as
parameters. The following equation illustrates a specific example
of a hopping pattern, where n_Vsc denotes the index of a
transmission frequency for a PRACH signal (e.g., a random access
preamble) before hopping, n_offset denotes a start offset of a
PRACH transmission band in an NB-IoT band, and n_Psc (i) denotes
the index of a frequency in a hopping unit at symbol point i. f_hop
(-1) may be set to 0, and c (k) may be a pseudo sequence, in which
an initial seed value may be set using a physical cell ID and/or a
hopping seed as parameters. N_sc denotes the number of subcarriers
in the PRACH transmission band.
n ~ Psc ( i ) = ( n ~ Vsc + f hop ( i ) ) mod ( N sc ) f hop ( i )
= ( f hop ( i - 1 ) + ( k = i 10 + 1 i 10 + 9 c ( k ) .times. 2 k -
( i 10 + 1 ) ) mod ( N sc - 1 ) + 1 ) mod N sc n ~ Vsc = n Vsc - n
offset n Psc ( i ) = n ~ Psc ( i ) + n offset [ Equation 1 ]
##EQU00001##
[0163] In a fourth example, frequency hopping between hopping units
is performed in a particular pattern within a particular frequency
region. The particular frequency region in which a PRACH signal
(e.g., a random access preamble) is transmitted may be divided into
a plurality of sub-regions (either in advance or via a higher-layer
signal). First hopping is frequency hopping between sub-regions
according to a first pattern, while second hopping is frequency
hopping between subcarriers in a sub-region according to a second
pattern. The first pattern and the second pattern may be
independently set. In a more specific example, the first pattern is
a pseudo random sequence-based pattern as illustrated in the third
example, which may change or select a sub-region. The second
pattern may be a form of performing mirroring (for example, 0, 1,
2, and 3 is converted into 3, 2, 1, and 0, respectively). Assuming
that a subcarrier spacing for a PRACH signal is 3.75 kHz, one
sub-region may include four subcarriers.
[0164] FIG. 14 illustrates a fourth example among a plurality of
examples of the third embodiment of the present specification.
[0165] As illustrated in FIG. 14, 12 subcarriers may be divided
into a plurality of sub-regions. For example, a first sub-region
may include four subcarriers with a subcarrier index k ranging from
0 to 3, a second sub-region may include four subcarriers with a
subcarrier index ranging from 4 to 7, and a third sub-region may
include four subcarriers with a subcarrier index ranging from 8 to
11. The number of subcarriers included in the sub-regions may be
set in advance or through a higher-layer signal. In addition, the
position of a subcarrier at which each sub-region starts, that is,
a subcarrier index or offset, may also be set in advance or through
a higher-layer signal.
[0166] First hopping may be selecting one of the plurality of
sub-regions and hopping to a frequency. Second hopping may be
performing frequency hopping between subcarriers in the selected
sub-region. That is, as illustrated in FIG. 14, the first hopping
may be hopping to a frequency in the third sub-region. The second
hopping may be hopping to a subcarrier within the third sub-region.
The second hopping may be performed every symbol. That is, the
second hopping may be performed every symbol i.
[0167] The following equation illustrates a specific example of a
hopping pattern, where n_Vsc denotes the index of a transmission
frequency for a PRACH signal (e.g., a random access preamble)
before hopping, n_offset denotes a start offset of a PRACH
transmission band in an NB-IoT band, and n_Psc (i) denotes the
index of a frequency in a hopping unit at symbol point i. f_hop
(-1) may be set to 0, and c (k) may be a pseudo sequence, in which
an initial seed value may be set using a physical cell ID and/or a
hopping seed as parameters. N_sc denotes the number of subcarriers
in the PRACH transmission band.
n ~ Psc ( i ) = ( n ~ Vsc + f hop ( i ) N sc sb + ( ( N sc sb - 1 )
- 2 ( n ~ Vsc mod N sc sb ) ) f m ( i ) ) mod ( N sc sb N sb ) f
hop ( i ) = ( f hop ( i - 1 ) + ( k = i 10 + 1 i 10 + 9 c ( k )
.times. 2 k - ( i 10 + 1 ) ) mod ( N sc - 1 ) + 1 ) mod N sc f m (
i ) = c ( 10 i ) n ~ Vsc = n Vsc - n offset n Psc ( i ) = n ~ Psc (
i ) + n offset [ Equation 2 ] ##EQU00002##
[0168] The above hopping pattern may be independently set for each
coverage extension level. Here, a parameter (e.g., the delta in the
first example, the hopping seed in the second example, or the like)
set through a higher-layer signal may be set for each coverage
level. Alternatively, a coverage extension level or a repetition
number may be used in setting a hopping pattern. Specifically, as
an initial seed for a hopping pattern, a physical cell ID and a
hopping seed may be simultaneously considered. An example for
simultaneous consideration may be aggregating the physical cell ID
and the hopping seed.
[0169] The index of the first or last subcarrier for a PRACH
according to the single-tone transmission method may be randomly
selected by a wireless device. Specifically, the index of the first
or last subcarrier for the PRACH in the case where the size of a
scheduled message (i.e., Msg3) transmitted in response to a random
access response is greater than a threshold value set in advance or
via a higher-layer signal (e.g., an SIB) and/or path loss is
smaller than a threshold value determined by a combination of
parameters signaled in advance or via a higher-layer signal (e.g.,
an SIB) may be different from that in other cases. Likewise, a
transmission method (e.g., a multi-tone transmission method or a
single-tone transmission method) for Msg3 may be subsequently
determined depending on the index of a representative or first
subcarrier for PRACH transmission according to the single-tone
transmission method. The PRACH according to the single-tone
transmission method may be limited to a PRACH transmitted last.
When code division multiplexing (CDM) is supported in PRACH
transmission according to the single-tone transmission method, the
index of the random access preamble may be considered along with
the index of the subcarrier. For example, a plurality of groups may
be created on the basis of a combination of a subcarrier index and
a random access preamble index. Then, the wireless device may
select a group according to the above conditions and may then
randomly select a subcarrier index and a random access preamble
index separately or as a combination from the group.
[0170] When a PRACH signal (e.g., a random access preamble)
according to the single-tone transmission method is triggered by a
(NB-) PDCCH command (order), DCI in the (NB-) PDCCH command may
include the position of the first or last subcarrier for
transmitting a PRACH according to the single-tone transmission
method. Accordingly, the wireless device may transmit a PRACH
signal (e.g., a random access preamble) according to the
single-tone transmission method using the position of the
subcarrier. A set of subcarrier positions to be indicated by the
PDCCH command may also be set via a higher-layer signal separately
from a contention-based PRACH. Alternatively, a frequency region
for transmitting a PRACH may be set separately.
[0171] Meanwhile, it may be expected that channel conditions are
similar in a sequence of one random access preamble, and thus a
hopping pattern needs to be considered in mapping a sequence of a
random access preambles across a plurality of PRACH resources. For
example, when there is a plurality of groups of frequency regions
for transmitting a PRACH signal, a sequence of a random access
preamble may be generated and mapped for each group. Specifically,
when a PRACH signal is repeatedly transmitted between frequency f1
and frequency f2, a sequence of a first random access preamble may
be generated and mapped for a resource at frequency f1, and a
sequence of a second random access preamble may be generated and
mapped for a resource at frequency f2.
[0172] Information on the time (for example, a subframe index or a
symbol index) at which transmission of a PRACH signal according to
the single-tone transmission method can start may be specified
through an SIB and may be set independently of a coverage extension
level.
[0173] FIG. 15 is a flowchart illustrating the operation of a
wireless device according to the fourth example of the third
embodiment of the present specification.
[0174] Referring to FIG. 15, an NB-IoT cell 200 transmits
sub-region information to a wireless device (e.g., an NB-IoT
device) 100 via a higher-layer signal. As described above, the
sub-region information may include one or more of the number of
sub-regions, the number of sub-carriers included in a sub-region, a
start offset, and a frequency index at symbol time i.
[0175] The wireless device (e.g., an NB-IoT device) 100 generates a
sequence for a random access preamble. The sequence may be
generated as described in Section I or III. For example, as
described above, the wireless device (e.g., an NB-IoT device) 100
may generate the sequence for the random access preamble using a
physical cell ID, identification information on a cell performing
an NB-IoT operation, or a seed value signaled through a
higher-layer signal.
[0176] Next, the wireless device (e.g., an NB-IoT device) 100 maps
the sequence to an RE, i.e., a subcarrier. Frequency hopping may be
performed during the mapping. The frequency hopping may be
performed in two stages. Specifically, the wireless device (e.g.,
an NB-IoT device) 100 performs first hopping and second hopping.
For the first hopping, the wireless device (e.g., an NB-IoT device)
100 may select one of a plurality of sub-regions and may then hop
to the selected sub-region. Subsequently, for the second hopping,
the wireless device (e.g., an NB-IoT device) 100 may perform
frequency hopping between subcarriers in the selected sub-region.
More specifically, for the second hopping, the wireless device
(e.g., an NB-IoT device) 100 may select one of subcarriers in the
selected sub-region and may hop to the selected subcarrier. Then,
the wireless device (e.g., an NB-IoT device) 100 may map the
sequence for the random access preamble to the selected
subcarrier.
[0177] Subsequently, the wireless device (e.g., an NB-IoT device)
100 transmits the random access preamble. An example in which the
random access preamble is mapped to the subcarrier may be the same
as illustrated in FIG. 14.
IV. Fourth Embodiment: Setup of Random Access Preamble Sequence
when CP Length and Symbol Length are Different
[0178] In introducing a PRACH according to the single-tone
transmission method in a next-generation system, it may be
considered that a subcarrier spacing is, for example, 3.75 kHz.
Further, a plurality of CP lengths may be introduced in the
next-generation system depending on the desired cell coverage
radius of a BS. In this section, it is assumed that the length of a
CP is 266.67 s (the reciprocal number of 3.75 kHz) or 66.67 .mu.s
(the reciprocal number of 15 kHz).
[0179] The length of a symbol forming a PRACH according to the
single-tone transmission method and the length of a CP may be
different depending on the length of a CP or may be set to be the
same. Phase discontinuity may be likely to occur as a symbol is
changed. In order to prevent the occurrence of phase discontinuity,
it may be considered to set a sequence for a random access preamble
applied to each symbol of a PRACH differently depending on the
length of a CP. For example, when the length of a CP is 266.67
.mu.s, which is the same as the length of a symbol for a PRACH
signal on the basis of a subcarrier spacing of 3.75 kHz, phase
continuity is guaranteed depending on a symbol switch even though a
sequence for a random access preamble is configured entirely with a
value of 1. However, when the length of a CP is 66.67 .mu.s, the
length of the CP is different from the length of a symbol, and thus
a PRACH transmission unit (unit including a CP and a plurality of
symbols) is changed. Accordingly, phase discontinuity may occur in
the previous unit and at the start point of each CP. Whether the
phase is continuous may be a factor that may affect complexity in
configuring a BS and/or a wireless device. In PRACH transmission in
the next-generation system, phase continuity can be guaranteed in
at least a certain period.
[0180] In a specific embodiment, it may be considered that a
sequence for a random access preamble is mapped to each group
including one CP and a plurality of symbols (e.g., five symbols).
That is, individual symbols in a group may be mapped to the same
value, and symbols in a different group may be mapped to a
different value. It is assumed that the length of the CP is 66.67
.mu.s (or 2048 T_s), a subcarrier spacing is be 3.75 kHz, and the
index of a hopping subcarrier mapped to each group is k0, k1, k2,
and the like. In this case, the sequence for the random access
preamble for each group may include a value determined by a
function of the index of a subcarrier to be mapped to the group.
For example, the sequence for the random access preamble to be
mapped to each group may have the following form.
1,exp(j2*pi*k1/4),exp(j2*pi*(k1+k2)/4),exp(j2*pi*(k1+k2+k3)/4), . .
. ,exp(j2*pi*Sum_{i=1 to n-1}(k_i)/4), . . . .
[0181] Values in each sequence may be repeated in order such that 1
is mapped to all symbols of the first group and the next value is
mapped to all symbols of the next group. The sequence for the
random access preamble is merely an example, and another sequence
for a random access preamble configured to satisfy phase continuity
may be extended from the idea of the present invention. For
example, setting a different sequence for each cell may be
considered in order to randomize inter-cell interference. In this
case, a sequence may be generated using a cell ID or an NB-IoT cell
ID. The sequence for the random access preamble may be reset after
a certain period or at a particular time to start from 1. A
criterion for resetting may be a plurality of subframes in the form
of a multiple of four, a single radio frame, or a plurality of
radio frames.
[0182] The aforementioned embodiments of the present invention can
be implemented through various means. For example, the embodiments
of the present invention can be implemented in hardware, firmware,
software, combination of them, etc. Details thereof will be
described with reference to the drawing.
[0183] FIG. 16 is a block diagram illustrating a wireless
communication system to implement embodiments of the present
specification.
[0184] A BS 200 includes a processor 201, a memory 202, and a
transceiver (or radio frequency (RF) unit) 203. The memory 202 is
coupled to the processor 201 and stores various pieces of
information for driving the processor 201. The transceiver (or RF
unit) 203 is coupled to the processor 201 and transmits and/or
receives a radio signal. The processor 201 implements the proposed
functions, procedures, and/or methods. In the aforementioned
embodiment, an operation of a BS may be implemented by the
processor 201.
[0185] A wireless device (e.g., an NB-IoT device) 100 includes a
processor 101, a memory 102, and a transceiver (or RF unit) 103.
The memory 102 is coupled to the processor 101 and stores various
pieces of information for driving the processor 101. The
transceiver (or RF unit) 103 is coupled to the processor 101 and
transmits and/or receives a radio signal. The processor 101
implements the proposed functions, procedures, and/or methods.
[0186] The processor may include Application-Specific Integrated
Circuits (ASICs), other chipsets, logic circuits, and/or data
processors. The memory may include Read-Only Memory (ROM), Random
Access Memory (RAM), flash memory, memory cards, storage media
and/or other storage devices. The RF unit may include a baseband
circuit for processing a radio signal. When the above-described
embodiment is implemented in software, the above-described scheme
may be implemented using a module (process or function) which
performs the above function. The module may be stored in the memory
and executed by the processor. The memory may be disposed to the
processor internally or externally and connected to the processor
using a variety of well-known means.
[0187] In the above exemplary systems, although the methods have
been described on the basis of the flowcharts using a series of the
steps or blocks, the present invention is not limited to the
sequence of the steps, and some of the steps may be performed at
different sequences from the remaining steps or may be performed
simultaneously with the remaining steps. Furthermore, those skilled
in the art will understand that the steps shown in the flowcharts
are not exclusive and may include other steps or one or more steps
of the flowcharts may be deleted without affecting the scope of the
present invention.
* * * * *